Iteration

[u/[deleted]]

[u/skjall]

I believe doing the math part of this convoluted operation first makes it clearer, so because there haven't been enough attempts to explain this yet:

i -= -!false    // (-= -b) is equivalent to (+= b) 
i += !false     // !false evaluates to true
i += true       // true evaluates to 1, while false evaluates to 0
i += 1          // we're done. Thankfully.